If we were to look at a piece of quartz, we generally will take
and we'll slice and dice, we'll lap and polish
down a piece of quartz. To make it functional, we put
a couple of electrodes across it. So now you have contacts, in order to make connection
to your electrical circuit. Well, if we apply a
voltage, say a DC voltage, through this wonderful
piezoelectric effect, you're going to change, you're gonna make a physical
change to that structure. It's going to move. How is it going to move? Well, that depends on how you built it. That depends on the modes you
see at the bottom corner. And the cut of the crystal,
where you place the electrodes, the spacing, all matter on
how that crystal will move. Well, we're trying to
store and release energy. Well, this is exactly
what you've done here. When you create a change,
a physical change, that crystal wants to simply return back to its original shape. It's not going to stay in that shape. And it does that very efficiently. You remove the voltage
on those electrodes, the crystal will fall
back into its normal shape that it was before. And vice versa, just as
much as your barbecue grill, or that cigarette lighter,
you induce a physical change. You have to release the button. You release the button,
and that's the "clang", out comes the voltage. This is the basic idea
behind our oscillators. Take an amplifier. Put a piece of quartz in series with it. So now what happens is, there's always noise within the system. Your regulators generate noise. There's just noise within
transistors, any type of gates. And that noise was
presented upon an amplifier. That amplifier increases
its signal on the output. It's fed into the quartz, and now the quartz sees a signal. It sees a voltage potential. And that voltage potential, through the piezoelectric effect, you're catching on here, is now making a deformation to the blank. And that deformation is
now wanting to release. Well, there's nothing
holding it in that position. The losses of the circuit are allowing it to start to release and relax
back to its normal position. That's the feedback mechanism. That's the release portion of the store and release energy. That releases energy
back into the circuit, which feeds back now into the amplifier. As long as the gain of that
amplifier is higher than all of the losses within the system, and that efficiency of that quartz, it will continue to increase in amplitude until limited by the circuit. That's the fundamental building block behind our oscillators. Now, this is generally put together by saying we have an
electrode, a piece of quartz, just as much as you did here. But we will deposit... We will deposit electrodes to the top and also to the bottom of that quartz. So you have an electrode on the top. You have an electrode on the bottom. These electrodes are epoxied,
to pins onto a header. They're glass fed through
to the outside world and then a cap is put on. It's either resistance-weld
or cold-welded. And that seals the
crystal inside the cavity. Now, you have a crystal
lead, here and here, and you also have a ground pin. You'll see that on many
oscillator applications where you have two crystal pins. It's not a positive/negative,
it's just two crystal leads. Well, a crystal is reversible. You can place it in any
direction that you want. And those are these two points. And that's the crystal that
goes into our oscillators. That's the basic building
block behind our oscillators. Thanks for watching! If you'd like to see more, head over to
microchip.com/missionassurance.
